Field of the Invention
The present invention relates to a data maintenance method of a data-storage device, and in particular to a data maintenance method related to triple-level cell units.
Description of the Related Art
Flash memory is considered a non-volatile data-storage device that uses electrical methods to erase and program itself. NAND Flash, for example, is often used in memory cards, USB flash devices, solid state devices, eMMCs, and other memory devices.
Flash memory such as NAND Flash uses a multiple-block structure to store data. Each block contains multiple pages. Due to the possibility of errors occurring during the flash memory data storage procedure, the system now encodes the original data then stores the encoded data into flash memory; when data is read, the encoded data is first extracted then decoded back into the original data. Even though the encoding and decoding procedure can decrease errors, this procedure is still limited in correcting parts of bit errors. When the number of errors exceeds a certain value, the flash memory controller realizes it is unable to decode the data effectively when proceeding with the decoding procedures. Moreover, the flash memory marks each of the unable pages or blocks as a bad page or bad block to eliminate the page or block. Therefore, memory space is reduced.